I question things which people take for granted. I would have been that kid who said the emperor was naked. In real life that kid would probably have been lynched, but I'll take my chances...
I believe truth inherently valuable, no matter how well intentioned the ideology it dispels may be.
I also write about random interesting things from my personal life.

The reasons I've heard make literally make no sense. It takes virtually NO EFFORT. Less than changing the channel with a remote (your hand doesn't
move as far, and there are only two choices instead of about 20) and far less
than the rest of driving. It doesn't force you to drive any slower, or to
take any additional driving time.

Your hand is already right there on the wheel. It takes about a second of
time, and moving one's hand about 3 inches.

If its just a lane change, not a turn, holding it down (or up) halfway prevents
it locking in place so you don't have to remember to shut it off. All
cars have that feature, for at least several decades (The "Happy"
Van, my first car which was built in 1968 had it)

Not only is it a simple courtesy to other drivers, it can also prevent
accidents.
Having driven both large commercial trucks, and tiny motorcycles, and having
been both the victim and cause of accidents, I am quite aware that, no matter
how much you are paying attention, there will be times when you miss someone.
If you signal, it gives them a few seconds more time to either get out of your
way, or honk to alert you of their presence.
I mentioned this to a friend of mine recently who pointed out that some drivers
will speed up when they see your signal, to prevent you from getting ahead of
them.
True enough, but personally I find not injuring or killing someone to be more
important than getting one single car length ahead. That extra car length
is likely, at most, to equal a tenth of a second difference in how quickly you get to
your destination.

Plus, of course, it is just respectful to those around you, who could plan
their own route more efficiently if they knew what you were planning to
do. For example, if you are on a four lane street, and the person in
front of you turns on the left signal, it gives you time to change lanes so that
you do not have to stop and wait behind them as they wait for an opening.

Wouldn't you appreciate that? So why wouldn't you extend the same
courtesy to others?

I suspect the general obnoxiousness of society is tied more than casually with
the significant expansion of commercialism in recent years. (For example,
naming public stadiums after a company is an entirely new phenomenon. We
are moving more than ever towards the idea that profit is the only sane reason
to do anything - but perhaps I will get into all that later)

I saw recently a motorcyclist who changed lanes every few seconds, cutting
directly in front of other vehicles, of course never signaling. If the traffic suddenly slowed, as happens without warning fairly
often, he would have had no way to avoid being rear-ended. I sort of
hoped I could see this happen. Unfortunately not this time. At
least in this case he was primarily just endangering himself.
I've also been seeing state highway patrol cars not bothering to
signal. Since their primary job is enforcing traffic laws, it implies
that as a society we have decided that enough people ignore the law it is in fact ok to
just ignore it... Sort of like with all traffic laws in NYC...